Thick gray sludge in the radiator can be caused by a buildup of corrosion, oil contamination, or a coolant leak mixing with debris. This sludge can block the radiator channels, leading to overheating and potential damage to the cooling system. It's important to flush the radiator and identify the root cause to prevent further issues.
Mineral sludge from tap water. A good radiator flushing will help and then use proper coolant to help keep the sludge building up and blocking the radiator.
Time to replace the head gasket.
You can use plain water to get sludge out of your car radiator. You can use Marvel Mystery oil to remove sludge from the oil pan.
the so called sludge is most likely some sort of cooling system sealant.
Time to replace the head gasket.
Car radiator flush sold as most automotive shops
Get one of those flush kits from an auto parts store.
leak calicium or other deposits plugging or restricting water passages exteriors fins rotted what does sludge mean in my radiator?
No You don't Need to change the water pump But you should change it and the thermostat if radiator was full of sludge. if not then no to both.
Sign of possible head gasket failure
I don't know for sure, but can't you just get a radiator flush kit to get out the sludge? It's worth asking the guy at the parts house about. In such extreme cases of cooling system sludge build up, I would take it to a shop for a professional flushing and cleansing. I would suggest a car radiator specialist type shop - they'll know how to NOT cause more damage to the system. See "Related Questions" below for more about flushing it yourself